Apparatus for growing a semiconductor crystal and method of growing the same

ABSTRACT

In an apparatus for growing a semiconductor crystal from semiconductor melt, a crucible retains the semiconductor melt. An electrode contacts with the semiconductor melt and applies current to the semiconductor melt. The electrode is formed by the same material as the semiconductor crystal.

BACKGROUND OF THE INVENTION

[0001] This invention relates to an apparatus for growing a semiconductor crystal and a method of growing the same, and in particular, to crystal growing technique for rotating semiconductor melt (or solution) by applying a magnetic field and current which cross to each other for the semiconductor melt.

[0002] A semiconductor crystal wafer used as a substrate of a super highly integrated electronic device is generally grown by the use of the known Czochralski method (thereinafter, abbreviated as a CZ method).

[0003] In this CZ method, the semiconductor crystal wafer is grown by pulling up a semiconductor single crystal from a rotating semiconductor melt in condition that the semiconductor single crystal is rotated in an opposite direction against the rotating direction of the semiconductor melt.

[0004] With such a structure, the semiconductor melt in retained in a crucible is heated by a cylindrical heater which is arranged around the crucible. In this condition, the crucible is rotated so as to put temperature distribution in the semiconductor melt into complete symmetrical state for a pulling-up axis of the semiconductor crystal.

[0005] In this event, it is necessary that a rotating center of the crucible and a symmetrical axis of heater arrangement correspond to the pulling-up axis of the semiconductor crystal in order to put the temperature distribution in the semiconductor melt into the symmetrical state for the axis.

[0006] In general, the axis for retaining the crucible is mechanically rotated in the conventional case.

[0007] However, a large apparatus is required to rotate the crucible with large size of crystal diameter. Consequently, the growth of a large semiconductor crystal gradually becomes difficult.

[0008] To solve such difficulty, suggestion has been made about an apparatus for growing a semiconductor crystal and a method of growing the same in the earlier application, namely, Japanese Patent Application No. Hei. 9-343261, which is not yet published.

[0009] This semiconductor crystal growing apparatus includes a device for applying a magnetic field for semiconductor melt during growth of a semiconductor crystal and another device for applying current perpendicular to the magnetic field for the semiconductor melt.

[0010] Further, an electrode which is immersed in the semiconductor melt and another electrode which supplies current to pull up a semiconductor crystal are used in the above semiconductor crystal growing apparatus.

[0011] In this semiconductor crystal growing apparatus, even when the semiconductor crystal having a large diameter of 30 cm or more is grown, the size of the apparatus is restricted to the minimum, and it is possible to accurately control rotation number.

[0012] However, when electrode material is dissolved into the semiconductor melt and the electrode material contains material except for the semiconductor melt and the growing semiconductor crystal, purity of the semiconductor melt and the growing crystal is degraded. This gives an adverse affect for the other impunity concentration distribution.

[0013] Moreover, the electrode is immersed into the semiconductor melt. In consequence, the rotation of the semiconductor melt is partially interrupted by the electrode. As a result, symmetric property of the rotation is also degraded.

SUMMARY OF THE INVENTION

[0014] It is therefore an object of this invention to provide an apparatus for growing a semiconductor crystal and a method of growing the same in which no contaminated impurity is mixed from an electrode into semiconductor melt (or solution).

[0015] It is another object of this invention to provide an apparatus for growing a semiconductor crystal and a method of growing the same in which rotation symmetric property of semiconductor melt is not degraded.

[0016] According to this invention, a crucible retains semiconductor melt. Further, an electrode contacts with the semiconductor melt and applies at least current to the semiconductor melt. With such a structure, the electrode is formed by the same material as the semiconductor crystal.

[0017] In this case, a magnetic filed is applied to the semiconductor melt in addition to the current. The magnetic filed is substantially perpendicular to the current. Herein, the current is applied between the semiconductor melt and the semiconductor crystal.

[0018] Moreover, a predetermined impurity is doped into the semiconductor crystal from the semiconductor melt. Under this circumstance, the semiconductor crystal does not contain the other impurity except for the doped impurity.

[0019] In this event, the semiconductor crystal may be a silicon single crystal. In this condition, the electrode is formed by the silicon single crystal. Under this circumstance, a predetermined impurity and oxygen are doped into the silicon single crystal from the semiconductor melt. In this case, the silicon single crystal does not contain the other impurity except for the doped impurity and the oxygen.

[0020] Alternatively, the semiconductor crystal may be a GaAs single crystal. In this event, the electrode is formed by the GaAs single crystal.

[0021] Further, the semiconductor crystal may be an InP single crystal. In this case, the electrode is formed by the InP single crystal.

[0022] More specifically, when the current is applied or supplied between the semiconductor melt and the semiconductor crystal during the growth, the same material as the semiconductor crystal to be grown is used as the electrode.

[0023] Consequently, no impurity is mixed from the electrode into the semiconductor melt, and further, unnecessary impurity is not mixed into the grown semiconductor crystal.

[0024] Further, the electrode contacts with the semiconductor melt at a higher position than the principal surface of the semiconductor melt by wettability. In consequence, the rotation of the semiconductor melt is not interrupted by the electrode. As a result, the rotating state of the semiconductor melt is not degraded.

[0025] Thereby, symmetric property for an axis of temperature distribution is enhanced, and concentration distribution of the dopant impurity trapped or doped in the semiconductor crystal becomes uniform in a radius direction.

[0026] Moreover, the concentration distribution of oxygen can be further equalized in the radius direction in the case of the silicon single crystal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a cross sectional view for explaining an insert position of an electrode when a semiconductor single crystal is grown by the use of the CZ method according to this invention;

[0028]FIG. 2 is a cross sectional view for explaining a contact position between an electrode and semiconductor melt when a semiconductor single crystal is grown by the use of the CZ method according to this invention;

[0029]FIG. 3 is a plane view for explaining insert positions of electrodes when a semiconductor single crystal is grown by the use of the CZ method according to an embodiment of this invention; and

[0030]FIG. 4 is a cross sectional view for explaining insert positions of electrodes when a semiconductor single crystal is grown by the use of the CZ method according to an embodiment of this invention

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0031] Hereinafter, description will be made about an embodiment of this invention referring to drawings.

[0032] First, description will be made about a method for applying or supplying current between a growing semiconductor crystal and semiconductor melt (or solution) retained in a magnetic field with reference to FIG. 1.

[0033] Herein, it is to be noted that peripheral devices, such as, a magnetic field applying device and a heater are abbreviated so as to emphasize main component portions.

[0034] A semiconductor single crystal 3 is pulled up from semiconductor melt 2 retained in a crucible 1 via a seed crystal 5. In this event, the seed crystal 5 is set at a tip portion of a pulling-axis 4 formed by a material having electric conduction.

[0035] Although the seed crystal 5 is coupled to the pulling-up axis 4 like the case of the crystal growth of the general CZ method, contact area between the seed crystal 5 and the pulling-up axis 4 becomes large to excellently keep the electric conduction.

[0036] With such a structure, an electrode 6 for supplying current between the growing semiconductor single crystal 3 and the semiconductor melt 2 in the crucible 1 is formed by the same material as the semiconductor single crystal 3 to be grown.

[0037] In this case, the electrode 6 contacts with the semiconductor melt 2 at a higher position than a principle surface 7 of the semiconductor melt 2, as illustrated in FIG. 2. Herein, it is to be noted that the reference numeral 8 in FIG. 2 denotes a contact surface between the electrode 6 and the semiconductor melt 2.

EXAMPLES

[0038] Subsequently, description will be made about examples of this invention.

[0039] As examples 1 through 4, a silicon solution of 0.3 Kg was manufactured in a quartz crucible having a diameter of 7.5 cm. In this condition, an electrode stick was contacted with the surface of the silicon solution. Under such a circumstance, a silicon single crystal having a diameter of 3 cm was grown.

[0040] In this case, the insert position of the electrode was set inside apart from an internal wall of the crucible with 1 cm, as shown in FIG. 1. In this event, boron was added into the semiconductor melt so that the grown silicon single crystal became P-type and had resistivity of 10 Ωcm, 1 Ωcm 0.1 Ωcm and 0.001 Ωcm, respectively.

[0041] Impurity elements in the grown crystal was analyzed by the use of the mass spectrometry. Thereby, it was confirmed whether or not the impurity was mixed in this sample to clarify effect of this invention.

[0042] Further, the concentration distribution of the dopant impurity in the semiconductor crystal was determined in the radius direction by the use of the spreading resistance method (namely, SR method).

[0043] Moreover, the concentration distribution of the oxygen in the semiconductor crystal was determined in the radius direction by the use of the scanning infrared absorption spectrometry (namely, FT-IR method).

[0044] During the growth of the crystal, the contact position between the electrode made by the silicon and the silicon solution was constantly observed from the side portion of the furnace by the use of the X-ray perspective.

[0045] Thereby, the relative position between the surface of the silicon solution and the silicon electrode was constantly kept constant.

[0046] In the examples 1 through 4, the contact position between the electrode and the solution was set to a higher position with 3 mm from the principal surface of the solution.

[0047] Table 1 totally indicates a value of the applied magnetic field, a value of the current, other conditions for growing the crystal, and results of the grown crystal.

[0048] Herein, concentration distributions of the dopant and the oxygen in the radius direction were determined by the following equation.

[(concentration at crystal center−concentration at crystal end)/concentration at crystal center]×100

[0049] TABLE 1 DOPANT OXYGEN MAGNETIC CRYSTAL CONCENT- CONCENT- FIELD ROTATION RESIS- RATION RATION STRENGTH CURRENT NUMBER TIVITY DISTRIBU- DISTRIBU- (T) (A) (rpm) (Ωcm) INPURITY TION (%) TION (%) EXAM- 0.01-0.5 0.01-10 1-10 10 NO 1.0 1.0 PLE 1 DETECTION EXAM- 0.01-0.5 0.01-10 1-10 1 NO 1.0 1.0 PLE 2 DETECTION EXAM- 0.01-0.5 0.01-10 1-10 0.01 NO 1.0 1.0 PLE 3 DETECTION EXAM- 0.01-0.5 0.01-10 1-10 0.001 NO 1.0 1.0 PLE 4 DETECTION

[0050] In examples 5 through 8, the silicon solution of 300 Kg was manufactured in the quartz crucible having the diameter of 70 cm. In this condition, the silicon single crystals which had resistivity of 10 Ωcm, 1 Ωcm, 0.1 Ωcm and 0.001 Ωcm and the diameter of 30 cm were grown from the silicon solution.

[0051] In this event, the silicon single crystal was grown in the condition that the silicon single crystal electrode, which had the diameter of 0.4 cm and the same composition as the silicon single crystal to be grown, was contacted with the surface of the silicon solution.

[0052] In these examples, the contact position between the electrode and the solution was kept to the height of 3 mm from principal surface of the solution. The arrangement of the electrodes is illustrated in FIGS. 3 and 4.

[0053] Table 2 totally indicates the value of the applied magnetic field, the value of the current, other conditions for growing the crystal, and results of the grown crystal. TABLE 2 DOPANT OXYGEN MAGNETIC CRYSTAL CONCENT- CONCENT- FIELD ROTATION RESIS- RATION RATION STRENGTH CURRENT NUMBER TIVITY DISTRIBU- DISTRIBU- (T) (A) (rpm) (Ωcm) INPURITY TION (%) TION (%) EXAMPLE 0.01-0.5 0.01-10 1-10 10 NO 0.5 0.5 5 DETECTION EXAMPLE 0.01-0.5 0.01-10 1-10 1 NO 0.5 0.5 6 DETECTION EXAMPLE 0.01-0.5 0.01-10 1-10 0.01 NO 0.5 0.5 7 DETECTION EXAMPlE 0.01-0.5 0.01-10 1-10 0.001 NO 0.5 0.5 8 DETECTION

[0054] In examples 9 through 12, the silicon single crystals which had resistivity of 10 Ωcm, 1 Ωcm, 0.1 Ωcm and 0.01 Ωcm and the diameter of 40 cm were grown using the quartz crucible having the diameter of 100 cm.

[0055] In this event, the crystal growth was carried out on the condition that three silicon electrodes, each of which had the diameter of 0.4 mm, were contacted with the surface of the silicon solution in the same manner as the example illustrated in FIG. 3.

[0056] In these examples, the contact position between the electrode and the solution was kept to the height of 3 mm from the principal surface of the solution.

[0057] Table 3 totally indicates the value of the applied magnetic field, the value of the current, other conditions for growing the crystal, and results of the grown crystal. TABLE 3 DOPANT OXYGEN MAGNETIC CRYSTAL CONCENT- CONCENT FIELD ROTATION RESIS- RATION RATION STRENGTH CURRENT NUMBER TIVITY DISTRIBU- DISTRIBU- (T) (A) (rpm) (Ωcm) INPURITY TION (%) TION (%) EXAMPLE 0.01-0.5 0.01-10 1-10 10 NO 0.5 0.5 9 DETECTION EXAMPLE 0.01-0.5 0.01-10 1-10 1 NO 0.5 0.5 10 DETECTION EXAMPLE 0.01-0.5 0.01-10 1-10 0.01 NO 0.5 0.5 11 DETECTION EXAMPLE 0.01-0.5 0.01-10 1-10 0.001 NO 0.5 0.5 12 DETECTION

[0058] It is found out from the above-mentioned examples that the silicon single crystal, which contains no impurity except for dopant impurity and oxygen, can be grown in the method according to this invention.

[0059] Further, non-uniform property of the oxygen concentration distribution and the dopant impurity concentration distribution in the silicon single crystal grown by the method according to this invention in the radius direction is equal to 1% or less. In consequence, it is found out that the solution rotates on the condition that the temperature distribution in the solution completely corresponds to the pulling-up axis of the semiconductor crystal.

[0060] Moreover, the silicon single crystals which had resistivity of 0.001 Ωcm and the diameters of 3.0 cm, 30.0 cm and 40.0 cm were grown without using the silicon electrode in comparison with the examples 1 through 12.

[0061] Table 4 represents material used as the electrode, analyzed result of impurity in the grown crystal, concentration distribution of the dopant impurity, and concentration distribution of the oxygen.

[0062] Herein, it is to be noted that the conditions of the crystal growth, which are not described in Table 4, are similar to the examples 1 through 12 including the arrangement of the electrodes.

[0063] In this case, the material of the electrode has different composition from the semiconductor single crystal to be grown in the comparative examples. Namely, the electrode is formed by the other material.

[0064] Consequently, it is difficult to keep the contact position at the higher position than the principal surface of the solution. Therefore, the electrode was contacted with the semiconductor melt at a deeper position than the principle surface of the solution with 3 mm to 5 mm. TABLE 4 DO- OXY- PANT GEN CON- CON- CEN- CEN- TRA- TRA- CRYS- CRUCI- TION TION TAL BLE DIS- DIS- DI- DI- ELEC- TRI- TRI- AME- AME- TRODE BU- BU- TER TER MA- IN- TION TION (cm) (cm) TERIAL PURITY (%) (%) COM- 3.0 7.5 CARBON CARBON 5.0 5.0 PARA- TIVE EX- AMPLE 1 COM- 3.0 7.5 TUNGS- TUNGS- 5.0 5.0 PARA- TEN TEN TIVE EX- AMPLE 2 COM- 30.0 75.0 CARBON CARBON 10.0 5.0 PARA- TIVE EX- AMPLE 3 COM- 30.0 75.0 TUNGS- TUNGS- 10.0 10.0 PARA- TEN TEN TIVE EX- AMPLE 4 COM- 40.0 100.0 CARBON CARBON 10.0 10.0 PARA- TIVE EX- AMPLE 5 COM- 40.0 100.0 TUNGS- TUNGS- 10.0 10.0 PARA- TEN TEN TIVE EX- AMPLE 6

[0065] It is found out that from these comparison results that the impurity except for the dopant impurity and the oxygen is mixed into the grown silicon single crystal when the material of the same composition as the semiconductor single crystal to be grown is not used as the electrode material.

[0066] Further, the electrode is placed at the deeper position than the principle surface of the solution. Thereby, the rotation of the solution is deformed at this position. Moreover, the symmetric property for the axis of the temperature distribution is also degraded.

[0067] As a result, it is confirmed that non-uniform property of the oxygen concentration distribution and the dopant impurity concentration distribution in the crystal in the radius direction is equal to 1% or more. Therefore, it is difficult to equalize the concentration distributions of the oxygen and the dopant impurity.

[0068] Subsequently, it is confirmed that this invention can be applied for the growth of the semiconductor crystal except for the silicon. Specifically, a GaAs single crystal having a diameter of 15 cm was grown from a p-BN (Pyrolytic-Boron Nitride) crucible having a diameter of 30 cm with the same electrode arrangement as the example 5, as the example 13.

[0069] In this event, the GaAs single crystal having the same composition as the GaAs single crystal to be grown was used as the electrode. In this time, the silicon was added with the desired quantity as the dopant so that the resistivity became 10 Ωcm.

[0070] Moreover, an InP single crystal having a diameter of 10 cm was grown from the p-BN crucible having a diameter of 20 cm using an InP single crystal having the same composition as the InP single crystal to be grown as the electrode material in the example 14.

[0071] In this time, antimony was added with the desired quantity as the dopant so that the resistivity became 10 Ωcm.

[0072] Table 5 represents conditions for growing the crystals of the examples 13 and 15, and the results of the grown crystals. TABLE 5 DOPANT KIND CRYSTAL/ ELEC- INPURITY CONCEN- OF CRUCIBLE TRODE EXCEPT TRATION CRYS- DIAMETER MA- FOR DISTRIBU- TAL (cm) TERIAL DOPANT TION (%) EX- GaAs 15.0/30.0 GaAs NO 0.5 AMPLE SINGLE DETEC- 13 CRYS- TION TAL EX- InP 15.0/30.0 InP NO 0.5 AMPLE SINGLE DETEC- 14 CRYS- TION TAL

[0073] It is found out from the results that the semiconductor single crystal containing no impurity except for the dopant impurity can be grown according to this invention when the semiconductor crystal except for the silicon is grown.

[0074] Further, it is confirmed that uniform semiconductor crystal having dopant concentration distribution of 1% or less in the radius direction can be grown.

[0075] In the meanwhile, it is to be noted that this invention is not limited to the above-mentioned examples with respect to the arrangement and structure of the electrode. This invention is applicable for all devices and all methods in which the material having the same composition as the semiconductor crystal to be grown is used as the electrode.

[0076] Moreover, it is clear that this invention is effective for the growth of the crystal material except for the semiconductor from principle examination. 

What is claimed is:
 1. An apparatus for growing a semiconductor crystal from semiconductor melt, comprising: a crucible which retains said semiconductor melt; and an electrode which contacts with said semiconductor melt and which applies at least current to said semiconductor melt; said electrode being formed by the same material as said semiconductor crystal.
 2. An apparatus as claimed in claim 1 , wherein: a magnetic filed is applied to said semiconductor melt in addition to the current.
 3. An apparatus as claimed in claim 2 , wherein: the magnetic filed is substantially perpendicular to the current.
 4. An apparatus as claimed in claim 1 , wherein: the current is applied between said semiconductor melt and said semiconductor crystal.
 5. An apparatus as claimed in claim 1 , wherein: a predetermined impurity is doped into said semiconductor crystal from said semiconductor melt, and said semiconductor crystal does not contain the other impurity except for the doped impurity.
 6. An apparatus as claimed in claim 5 , wherein: said semiconductor crystal is a silicon single crystal, said electrode is formed by the silicon single crystal.
 7. An apparatus as claimed in claim 6 , wherein: a predetermined impurity and oxygen are doped into said silicon single crystal from said semiconductor melt, and said silicon single crystal does not contain the other impurity except for the doped impurity and the oxygen.
 8. An apparatus as claimed in claim 7 , wherein: the oxygen has concentration distribution in a radius direction of said silicon single crystal, and the concentration distribution is substantially uniform along the radius direction.
 9. An apparatus as claimed in claim 1 , wherein: said semiconductor crystal is a GaAs single crystal, and said electrode is formed by the GaAs single crystal.
 10. An apparatus as claimed in claim 1 , wherein: said semiconductor crystal is an InP single crystal, and said electrode is formed by the InP single crystal.
 11. An apparatus for growing a semiconductor crystal from semiconductor melt having a principal surface, comprising: a crucible which retains said semiconductor melt; an electrode which applies at least current to said semiconductor melt; a partial electrode portion which contacts with the principal surface said partial electrode portion being formed by the same material as said semiconductor crystal.
 12. An apparatus as claimed in claim 11 , wherein: a magnetic filed is applied to said semiconductor melt in addition to the current.
 13. An apparatus as claimed in claim 12 , wherein: the magnetic filed is substantially perpendicular to the current.
 14. An apparatus as claimed in claim 11 , wherein: the current is applied between said semiconductor melt and said semiconductor crystal.
 15. An apparatus for growing a semiconductor crystal from semiconductor melt having a principal surface, comprising: a crucible which retains said semiconductor melt; and an electrode which applies at least current to said semiconductor melt; and said electrode contacting with said semiconductor melt at a higher position than the principal surface.
 16. An apparatus as claimed in claim 15 , wherein: said electrode is formed by the same material as said semiconductor crystal.
 17. An apparatus as claimed in claim 15 , wherein: said electrode and the higher position are constantly kept within a relative positional relationship.
 18. An apparatus as claimed in claim 15 , wherein: said electrode has a partial electrode portion, and said partial electrode portion contacts with the semiconductor melt at the higher position.
 19. An apparatus as claimed in claim 18 , wherein: said partial electrode portion is formed by the same material as said semiconductor crystal.
 20. An apparatus as claimed in claim 15 , wherein: a magnetic filed is applied to said semiconductor melt in addition to the current.
 21. An apparatus as claimed in claim 18 , wherein: the magnetic filed is substantially perpendicular to the current.
 22. An apparatus as claimed in claim 15 , wherein: the current is applied between said semiconductor melt and said semiconductor crystal.
 23. A method of growing a semiconductor crystal from semiconductor melt having a principal surface, comprising the steps of: retaining said semiconductor melt in a crucible; contacting an electrode with said semiconductor melt at a higher position than the principal surface; applying at least current to said semiconductor melt via said electrode; and pulling up said semiconductor crystal from said semiconductor melt via a seed crystal on the condition that the current is applied to said semiconductor melt and said semiconductor melt is rotated; said electrode being formed by the same material as said semiconductor crystal.
 24. A method as claimed in claim 23 , wherein: a magnetic filed is applied to said semiconductor melt in addition to the current.
 25. A method as claimed in claim 23 , wherein: the magnetic filed is substantially perpendicular to the current.
 26. A method as claimed in claim 23 , wherein: the current is applied between said semiconductor melt and said semiconductor crystal.
 27. A method as claimed in claim 23 , further comprising the following step: constantly keeping said electrode and the higher position within a relative positional relationship.
 28. A method as claimed in claim 23 , wherein: the pulling up step is carried out so that the rotation of said semiconductor melt is not disturbed by said electrode. 